1. Field of the Invention
The invention relates to the field of lighter-than-air and/or simi-buoyant vehicles and, in particular, to vehicles having solar panels for generating electrical power.
2. Description of Related Art
There are basically two main types of fully lighter-than-air vehicles; the ridged type or as it is more commonly called the xe2x80x9cdirigiblexe2x80x9d and the non-ridged type or xe2x80x9cblimpxe2x80x9d. Blimps basically comprise a single or multi-number of non-ridged gas bags wherein internal inflation pressure is used to form the external shape of the vehicle. A typical example of this design is found in U.S. Pat. No. 4,265,418 xe2x80x9cElongated Inflatable Structures For Flying Device Bodiesxe2x80x9d by M. Eymard. The other basic type of lighter-than-air vehicle is-the ridged design wherein an internal support structure is covered with a flexible material that serves as the outer skin. The vehicle may consist of a single gas chamber wherein the outer skin serves as the xe2x80x9cgas bagxe2x80x9d or can have numerous internal gas bags. An example of this concept can be found in U.S. Pat. No. 4,591,112 xe2x80x9cVectored Thrust Airshipxe2x80x9d by F. N. Piasecki, et al.
These two examples are true lighter-than-air vehicles in that the gas filled balloon generates all the lift. However, having the external contour of the vehicle in an aerodynamic lift producing shape can reduce the overall size of such vehicles and generally cost, for any given payload. Such aircraft are not totally buoyant and take off in a manner similar to a conventional aircraft. In such designs, it is common practice to use a ridged internal frame (the dirigible concept) in order to maintain the proper contour. For example U.S. Pat. No. 3,486,719 xe2x80x9cAirshipxe2x80x9d by J. R., Fitzpatick, Jr. While the Fitzpatick, Jr. design uses a ridged skin; most use a flexible gas bag with an internal frame structure. Of course there are non-ridged designs such as disclosed in U.S. Pat. No. 2,778,585 xe2x80x9cDynamic Lift Airshipxe2x80x9d by D. B. Tschudy. D. B. Tschudy""s design includes a multi-lobe gas bag with a general aerodynamic shape.
High altitude long-duration solar powered airships have been proposed for both commercial and military applications. For example, station keeping lighter-than-air vehicles have been proposed for cellular telephone applications. Military applications also include telecommunication applications as well as intelligence gathering. In most such applications, long duration station keeping is essential. Thus electrical energy generated using solar arrays or photo-voltaic cells to power the vehicle has been considered. U.S. Pat. No. 4,534,525 xe2x80x9cEvacuated Balloon For Solar Collectionxe2x80x9d by E. E. Bliamptis disclosed a blimp concept wherein solar energy is collected through a transparent portion of the of the structure and reflected from internally positioned shaped surfaces to the to solar collectors. Such a design requires transparent material, which may not be structurally efficient. It may also have undesirable thermal effects on the lifting gas. It also limits the orientation of the vehicle. Another example can be found in U.S. Pat. No. 4,788,629 xe2x80x9cFlying Object For Collecting Solar Raysxe2x80x9d by K. Mori. Here the vehicle is disc shaped and maintains its position by a propulsion system. Solar energy is collected by a solar collecting device and guided through an optical conductor into the interior of the vehicle. Again, as in the previous example, maintaining optimum position in relationship to the sun can be difficult and limits orientation of the vehicle.
Most all spacecraft are solar powered. In such vehicles, as well as on the ground, the solar panels are rotatable so that an optimum angle can be maintained between the solar panels and the sun. An example can be found in U.S. Pat. No. 3,817,477 xe2x80x9cDeployable Annular Solar Array: by E. M Luther, et al. Far more common is to just mount the solar panels on large rotatable booms. However, these systems are not particularly advantages for use on a lighter-than-air type vehicle. Several experimental propeller driven aircraft have been flown incorporating solar panels on the wings, including long endurance high altitude aircraft
Thus, it is a primary object of the invention to provide an at least partially buoyant vehicle that is at least partially powered by solar power.
It is another primary object of the invention to provide an at least partially buoyant vehicle that is at least partially powered by solar power wherein the solar panels can be adjusted to maximize the absorption of sunlight.
It is a further object of the invention to provide an at least partially buoyant vehicle that is at least partially powered by solar power wherein the solar panels can be adjusted to maximize the absorption of sunlight and which does not compromise the flying qualities of the vehicle or the performance of the payload, or mission equipment.
It is a still further object of the invention to provide an at least partially buoyant vehicle that is at least partially powered by solar power and minimizes the amount of photo-voltaic cells required.
The invention is at least a partially buoyant vehicle that is solar powered. In detail, the vehicle includes a gas-containing structure having an outer contoured surface. At least one solar panel assembly is mounted to the outer surface of gas-containing structure, the solar panel movable over a portion of the surface of gas-containing structure. A drive system is provided for moving the at least one solar panel assembly over the outer surface of the gas-containing structure. A track assembly is mounted on the surface of the gas-containing structure for guiding the at least one solar panel assembly over the surface. Preferably, the at least one solar panel assembly in the form of a flexible strip having first and second ends is movable along the surface about the longitudinal axis of the vehicle.
Preferably, the drive system to move the at least one solar panel assembly over the surface of the gas-containing structure includes first and second motors mounted on the surface of the gas-containing structure on each side thereof. The first and second motors drive reels incorporating cables attached to each end of the at least one solar panel assembly. Thus when the motors are actuated, the at least one solar panel assembly can be moved over the surface of the gas containing structure so that the position of the at least one solar panel assembly is always optimally position in relation to the sun maximizing power generation. Alternately, a single motor with a reel mounted on the surface of the vehicle could be used with a cable wrapped about the reel with the ends coupled to each end of the solar panel.
To aid in the movement of the at least one solar panel assembly and to insure that the at least one solar panel assembly remains in position on the surface of the gas bag, a plurality of guide assemblies are mounted on the surface of the gas-containing structure. In addition, a friction reducing surface is applied to the gas-containing structure along its path of the at least one solar panel assembly, to reduce frictional forces. Of course, the friction reducing material could be applied to the underside of the solar panel, or to both surfaces.
The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description in connection with the accompanying drawings in which the presently preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for purposes of illustration and description only and are not intended as a definition of the limits of the invention.